Title: Method and apparatus for assessing neural activation.Abstract: Various embodiments concern sensing a LFP signal from one or more electrodes, measuring the amplitude of the signals over a period of time, and calculating a plurality of variance values from the amplitude, wherein each of the variance values correspond to the variance of the amplitude for a different interval of time of the period of time with respect to the other variance values. Such embodiments may further include assessing the relative level of neural activation of an area of the brain based on the variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower. ...

TECHNICAL FIELD

BACKGROUND

Implantable medical devices, such as electrical stimulation devices, may be used in different therapeutic applications, such as for deep brain stimulation, spinal cord stimulation, pelvic stimulation, gastric stimulation, peripheral nerve stimulation, or functional electrical stimulation of a target tissue site within a patient. An electrical stimulation device may be used to treat a variety of symptoms or conditions of a patient, such as chronic pain. In some therapy systems, an implantable electrical stimulator delivers electrical therapy to a target tissue site within a patient with the aid of one or more electrodes, which may be deployed by medical leads.

SUMMARY

In general, the disclosure relates to methods, systems, and devices for assessing neural activation and further controlling therapy based on the assessment of neural activation.

Various embodiments concern methods for assessing activation of a brain, comprising sensing one or more bioelectrical signals from one or more electrodes in contact with or proximate a brain, measuring the amplitude of the one or more bioelectrical signals over a period of time, calculating a plurality of variance values from the amplitude of the one or more bioelectrical signals, each of the variance values of the plurality corresponding to the variance of the amplitude for a different interval of time of a period of time with respect to the other variance values of the plurality of variance values, and assessing the relative level of neural activation of an area of the brain based on the plurality of variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower and wherein sensing, measuring, calculating, and assessing are each performed at least in part by control circuitry. In some of the method embodiments, assessing the relative level of neural activation of the area of the brain comprises estimating the functional synaptic volume of the area of the brain. In some of the method embodiments, assessing the relative level of neural activation of the area of the brain comprises comparing the plurality of variance values and determining whether the variance has increased or decreased within the period of time, wherein the level of neural activation is assessed to have increased within the period of time if the variance increased and the level of neural activation is assessed to have decreased within the period of time if the variance decreased. In some of the method embodiments, assessing the relative level of neural activation comprising setting one or both of a variance baseline and a variance range based on at least some of the plurality of variance values, and determining whether one or more of the variance values deviate from one or both of the variance baseline and the variance range.

Some of the method embodiments further comprise tracking the effectiveness of a therapy based on the assessment of the relative level of neural activation of the area of the brain. In some cases, therapy is indicated to be at least somewhat effective if the variance of the amplitude of the one or more bioelectrical signals increases relative to a baseline variance associated with a lesser amount of the therapy or no therapy. Some embodiments further comprise titrating a drug therapy based on the assessment of the relative level of neural activation of the area of the brain. Some embodiments further comprise titrating an electrical stimulation therapy based on the assessment of the relative level of neural activation of the area of the brain.

Some of the method embodiments further comprise tracking a brain condition based on the assessment of the relative level of neural activation of the area of the brain, wherein the brain condition is one or both of an injury and a disease. Some of the method embodiments comprise determining the location of the one or more electrodes in the brain based on the assessment of the relative level of neural activation of the area of the brain. In some of the method embodiments, the one or more bioelectrical signals comprise local field potential signals.

Various embodiments concern a system comprising: a lead; one or more electrodes that are on the lead and are configured to sense bioelectrical activity; and control circuitry configured to sense one or more bioelectrical signals using the one or more electrodes, measure the amplitude of the one or more bioelectrical signals over a period of time, calculate a plurality of variance values from the amplitude of the one or more bioelectrical signals, each of the variance values of the plurality corresponding to the variance of the amplitude for a different interval of time of a period of time with respect to the other variance values of the plurality of variance values, and assess the relative level of neural activation of an area of a brain based on the plurality of variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower.

In some embodiments, the control circuitry is configured to assess the relative level of neural activation of the area of the brain by estimating the functional synaptic volume of the area of the brain. In some embodiments, the control circuitry is configured to assess the relative level of neural activation of the area of the brain by comparing the plurality of variance values and determining whether the variance has increased or decreased within the period of time, wherein the level of neural activation is assessed to have increased within the period of time if the variance increased and the level of neural activation is assessed to have decreased within the period of time if the variance decreased. In some embodiments, the control circuitry is configured to assess the relative level of neural activation of the area of the brain by setting one or both of a variance baseline and a variance range based on at least some of the plurality of variance values, and determining whether one or more of the variance values deviate from one or both of the variance baseline and the variance range. In some embodiments, the control circuitry is configured to track the effectiveness of a therapy based on the assessment of the relative level of neural activation of the area of the brain. In some embodiments, the control circuitry is configured to track a brain condition based on the assessment of the relative level of neural activation of the area of the brain and provide an output on a display based on the tracking of the brain condition, wherein the brain condition is one or both of an injury and a disease.

In some embodiments, therapy is indicated to be at least somewhat effective if the variance of the amplitude of the one or more signals increases relative to a baseline variance associated with a lesser amount of the therapy or no therapy. In some embodiments, the control circuitry is configured to titrate a drug therapy based on the assessment of the relative level of neural activation of the area of the brain. In some embodiments, the control circuitry is configured to titrate an electrical stimulation therapy based on the assessment of the relative level of neural activation of the area of the brain.

In some embodiments, the control circuitry is configured to determine the location of the one or more electrodes in the brain based on the assessment of the relative level of neural activation of the area of the brain and indicate the location on a display. In some cases, the one or more signals comprise local potential signals.

Various embodiments concern a system for assessing activation of a brain, comprising means for sensing one or more bioelectrical signals from a brain; means for measuring the amplitude of the one or more bioelectrical signals over a period of time, means for calculating a plurality of variance values from the amplitude of the one or more bioelectrical signals, each of the variance values of the plurality corresponding to the variance of the amplitude for a different interval of time of a period of time with respect to the other variance values of the plurality of variance values, and means for assessing the relative level of neural activation of an area of the brain based on the plurality of variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower.

Various embodiments concern a physically embodied computer-readable medium comprising processor executable program instructions that, when executed by the processor, cause a medical device to: sense one or more bioelectrical signals from a brain; measure the amplitude of the one or more bioelectrical signals over a period of time; calculate a plurality of variance values from the amplitude of the one or more bioelectrical signals, each of the variance values of the plurality corresponding to the variance of the amplitude for a different interval of time of a period of time with respect to the other variance values of the plurality of variance values; and assess the relative level of neural activation of an area of the brain based on the plurality of variance values, wherein the area of the brain is assessed to have a relatively higher level of neural activation when the variance is relatively higher and the area of the brain is assessed to have a relatively lower level of neural activation when the variance is relatively lower.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

DETAILED DESCRIPTION

The human brain is composed of billions of neurons electrically interconnected and organized into various areas to perform a variety of functions. The neurons of a particular area can be associated with one or more different brain functions. These areas can overlap and share networks of neurons. The electrical activation of neurons is responsible for the function of the brain and communication amongst the various areas of the brain along networks. It is generally thought that the activation of numerous neurons is necessary to carryout each brain function. Moreover, for various areas of the brain, many of the neurons in one or more areas of the brain will depolarize, sometimes in synchrony, in an effort to carryout a function supported by the one or more areas. The activation of neurons can be measured as a bioelectrical signal, such as a local field potential (LFP), electroencephalogram (EEG), magnetoencephalography (MEG), and/or electrocorticogram (ECoG) signal, among other measurement techniques.

Certain neurological and psychiatric disorders, as well as brain injuries, can be characterized by deficits in large-scale integration across distributed brain networks. Subsequent to a variety of neurological injuries (e.g., stroke) and diseases (e.g., Parkinson\'s disease) the normal patterns of neuronal activity can be disrupted, possibility in multiple brain regions, due to cell degeneration and death of neurons or other consequences of injury and disease. Such damage can weaken whole areas of the brain and inhibit brain areas in properly carrying out their various functions. Moreover, damage from disease or injury can weaken the connections between brain areas and compromise the ability of brain networks to communicate and coordinate.

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20121025|20120271189|assessing neural activation|Various embodiments concern sensing a LFP signal from one or more electrodes, measuring the amplitude of the signals over a period of time, and calculating a plurality of variance values from the amplitude, wherein each of the variance values correspond to the variance of the amplitude for a different interval |Medtronic-Inc